A large number of people, including those suffering from conditions such as diabetes use some form of infusion therapy, such as daily insulin infusions to maintain close control of their glucose levels. There are two principal modes of daily insulin therapy. The first mode includes syringes and insulin pens. These devices are simple to use and are relatively low in cost, but they require a needle stick at each injection, typically three to four times per day. The second mode includes infusion pump therapy, which entails the purchase of an insulin pump that lasts for about three years. The initial cost of the pump can be significant, but from a user perspective, the overwhelming majority of patients who have used pumps prefer to remain with pumps for the rest of their lives. This is because infusion pumps, although more complex than syringes and pens, offer the advantages of continuous infusion of insulin, precision dosing and programmable delivery schedules. This results in closer blood glucose control and an improved feeling of wellness.
The use of an infusion pump requires the use of a disposable component, typically referred to as an infusion set or pump set, which conveys the insulin from a reservoir within the pump into the skin of the user. An infusion set typically consists of a pump connector, a length of tubing, and a hub or base from which a hollow infusion needle or cannula extends. The hub or base has an adhesive which retains the base on the skin surface during use, which may be applied to the skin manually or with the aid of a manual or automatic insertion device.
Currently, most insulin infusion sets deliver insulin to the subcutaneous layers of skin using either fixed metal needles or flexible plastic cannulas. Such infusion sets typically deliver insulin 4-10 mm below the skin surface. However, the upper 3 mm of skin surface, the intradermal space, facilitates better drug absorption. Unfortunately, due to the relative thinness of the intradermal layer, inserting a needle at such depth and maintaining an infusion site over an extended period of time within this narrow band is difficult.
One technique to provide intradermal injection is the Mantoux technique. As known to those skilled in the art, the Mantoux technique is typically used when administering tuberculosis tests. Skilled practitioners first stretch taut the selected area of skin between the thumb and forefinger, and then insert the needle slowly, bevel upward, at an angle of 5 to 15 degrees to the skin surface. The practitioner then advances the needle through the epidermis approximately 3 mm, releases the stretched skin, and injects the medicament. However, even where intradermal delivery can be accomplished with the standard Mantoux technique, this method is highly variable and subject to user error.
Most insulin infusion sets typically do not provide any features to isolate the inserted needle from shock or other external forces. Since those infusion sets typically deliver insulin 4-10 mm below the skin surface, shock or other external forces to the set have less effect on the deeper inserted needle. However, where an attempt is made to target the upper 3 mm of skin surface, any shock or movement of the set can adversely affect needle insertion and infusion performance.
Still further, most insulin sets have inserters that can result in skin surface “tenting” during needle insertion, where the skin surface is deflected somewhat prior to or during needle insertion which makes precisely targeting the upper 3 mm of skin surface difficult.
Inserted needles can be moved when a large force is exerted on the infusion set or when the adhesive of the adhesive patch fails. A bend radius of the inserted needle can be as small as 0.005 inches, which can lead to a needle fracture after between 2-10 bend cycles. Accordingly, a need exists for increasing the bend radius of an inserted needle to prevent needle deformation and fracture.
In general, a need exists for an infusion set that can deliver content to the upper 3 mm of skin surface, the intradermal space, to facilitate better drug absorption, while maintaining a degree of comfort to the user.